If you have a problem related to the National Electrical Code (NEC), are experiencing difficulty in understanding a Code requirement, or are wondering why or if such a requirement exists, ask Charlie, and he will let the Code decide. Questions can be sent to firstname.lastname@example.org. Answers are based on the 2011 NEC.
Missing home grounding component
The electrician who originally did the electrical grounding of my home (new in 2003) attached the wire from the breaker panels to my copper plumbing inside the basement. He attached it at the copper water line coming out of the well tank in the basement with a jumper over the valve. I have confirmed with the company that dug the well that the line from the house to the well is flexible plastic. They also ran one rod into the ground and connected it to the incoming electrical box from the utility company. What am I missing?
Apparently, you do not have 10 feet of metal underground water pipe to be used as a part of the grounding-electrode system. The copper plumbing inside the basement is a part of the interior water piping system and must be connected to the equipment-grounding conductor. This was done by connection to the ground bar in the service panel. In the absence of a metal underground water pipe, the grounding electrode the installer chose was a ground rod. Based on the Code in effect at that time, the ground rod needed to be tested to ensure a resistance of 25 ohms to ground or less. An alternative permitted to the test for resistance-to-ground was to install a second ground rod. The installer probably did neither, and the installation may be in violation of the Code. Installing a second ground rod in accordance with 250.53(A)(2) should bring your installation up to Code.
Adequate well grounding
My well casing is rigid metal, so I was thinking of also running the grounding-electrode conductor to the well but have been told it isn’t necessary if I have two ground rods. Is this true?
A metal well casing is not required to be a part of the grounding-electrode system; however, the metal well casing is required to be connected to the well pump circuit equipment-grounding conductor. Based on the 2011 NEC 250.50, a grounding--electrode system must be formed by bonding together all of the grounding electrodes that are present at each building. If this is a new residential building you are working on, there are probably only two electrodes present—a metal underground water pipe to the well [250.52(A)(1)] and a concrete-encased electrode [250.52(A)(3)]. The metal underground water pipe electrode requires a supplemental electrode [250.53(D)(2)], and the -concrete-encased electrode can serve as this supplemental electrode. If the concrete-encased electrode is present and you missed the connection to it before it was poured, you are still required to connect to it—whatever it takes. The two ground rods aren’t going to cut it by themselves.
Grounding well casing at residence
Is it required to ground the well casing at a residence if the water line is PVC?
I think the metal well casing is pretty well grounded by its contact with the earth. Article 100 defines “grounded” as being “Connected to earth or to some conducting body that serves in place of the earth.” However, unless the metal well casing is bonded to the -equipment-grounding (bonding) conductor, there is no path for ground-fault current other than through the earth. Of course, this is a path of very high resistance and is prohibited by 250.4(A)(5) and 250.54, which both state, “the earth shall not be considered as an effective ground-fault current path. NEC 250.112(M) requires that where a submersible pump is used in a metal well casing, the metal well casing shall be bonded to the equipment-grounding (bonding) conductor of the circuit that supplies the submersible pump.
Conductors sharing a neutral
If you share a neutral with two hot conductors, do you have to tie the breakers together with a breaker tie? My co-worker said it has to be done no matter the situation, and I disagree. I think tying the breakers together is not required in commercial installations, but in residential installations, when using 14–3 or 12–3 to carry two circuits to an area, I think you may have to use a breaker tie.
When you share a neutral with two or more ungrounded conductors that have a voltage between them, you have a multiwire branch circuit [210.4(A)]. Each multiwire branch circuit must be provided with a means to simultaneously disconnect all ungrounded conductors at the point where the circuit originates [210.4(B)]. These requirements apply to all installations. The commonly used 3-wire home runs must be connected to circuit breakers that will simultaneously disconnect both circuits. This can be accomplished using a two-pole circuit breaker or two single-pole circuit breakers with an identified handle tie.
Using an enclosure as a raceway
The contractor has provided three separate disconnect switches for three heat pumps. He has extended the three circuits’ wiring through each disconnect switch, one to the other. I contend that the installation is in violation of NEC Article 404 Switches [404.3(B)], which states, “Used as a Raceway. Enclosures shall not be used as junction boxes, auxiliary gutters, of raceways for conductors feeding through...”. The contractor responded that he is in compliance because of the last sentence, which states, “… unless the enclosure complies with 312.8.” My contention is that 312.8 would not be applicable because it is under Article 312, Cabinets, Cutout Boxes and Meter Socket Enclosures, of which this is not.
A disconnect switch is designed to be factory--mounted in an enclosure, which can be either a cutout box designed for surface-mounting or a cabinet designed for either flush- or surface-mounting. Both cabinets and cutout boxes are covered in 312.8. If there is adequate space within the enclosure for the feed-through conductors, the installation meets the minimum requirements of the Code. The reference to 312.8 from 404.3(B) makes the provisions of 312.8 applicable. There is a new requirement in the 2011 NEC Section 312.8(3) that calls for a warning label that identifies the closest disconnecting means for any feed-through conductors in the enclosure. This will be a great safety enhancement for workers.
Receptacles in accessory buildings
I am trying to complete a 1,460-square-foot detached workshop in my backyard and just failed the final electrical inspection. The inspector stated all receptacles inside and out need to be tamper--resistant. I can drive cars into the building since the primary use will be working on cars, motorcycles, etc. I am trying to figure out now if tamper-resistant receptacles are required per the NEC in my free-standing detached (accessory building).
NEC 410.12 requires, in all areas specified in 210.52, all nonlocking type 125-volt (V), 15- and 20-ampere (A) receptacles to be listed tamper-resistant receptacles. NEC 210.52(G) requires at least one receptacle outlet in a detached accessory building. Based on the 410.12 requirement, all nonlocking type 125V, 15- and 20A receptacles installed in accessory buildings must be listed tamper-resistant receptacles.
Code edition discrepancy
In the March 2011 Code FAQs question, “What can I use,” you responded that ampacity adjustment is not required. The reader stated that he had nonlinear loads. Article 310.15(B)(4)(c) states, “Where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor. The neutral conductor shall, therefore, be considered a current carrying conductor.” I feel you should have let the reader know that, if a major portion of the load consisted of nonlinear loads, he needed to adjust. Also you reference 310.15(B)(3)(a) for ampacity adjustment. Shouldn’t the reference have been 310.15(B)(2)(a)?
Thanks for commenting. I believe the question acknowledged that there were nonlinear loads and that derating was required. All of the Code references in the answer are correct. Code FAQs answers are based on the 2011 NEC. I know it is difficult when you are using an earlier edition of the Code, but purchasing the latest edition of the NEC is certainly practical for electrical installers.
Installing cables above ceiling tiles
I understand that most wiring will be accomplished by following joists either parallel or perpendicular, but is there a Code requirement for that? As long as the cable (in this case, a Cat 5 cable) is supported correctly, why couldn’t a diagonal run be used?
There are no specific NEC requirements regarding the manner in which cable should be run above ceiling tiles with respect to the ceiling joists. I believe the performance of Cat 5 cable is adversely affected by the length of the run and diagonal may be a better way to install it. Check out required compliance rules for cable installation in 300.11(A).
TROUT answers the Code Question of the Day on the NECA website. He can be reached at email@example.com.